Hollow fiber fabrics

ABSTRACT

The present invention is directed to fibrous fabric comprising hollow fibers. Preferably, the fibrous fabrics will have an opacity greater than a fibrous fabric with an equivalent basis weight and made with the same material and the same fiber diameter. The fibrous fabric comprising hollow fibers may also have an opacity greater than a higher basis weight fibrous fabric containing the same material and having an equivalent fiber diameter and the same number of fibers. The perimeter of the hollow region of the hollow fibers is substantially non-concentric to the outer perimeter of the hollow polymeric fibers. The hollow fibers can be monocomponent and multicomponent, as well as monoconstituent or multiconstituent. These hollow fibers are then consolidated into woven and nonwoven fibrous fabrics that are then converted into articles.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/438,350, filed Jan. 7, 2003.

FIELD OF THE INVENTION

[0002] The present invention relates to fibrous fabrics containinghollow fibers and processes of making hollow fibers.

BACKGROUND OF THE INVENTION

[0003] Commercial woven and nonwoven fabrics are typically comprised ofsynthetic polymers formed into fibers. These fabrics are typicallyproduced with solid fibers that have a high inherent overall density,typically 0.9 g/cm³ to 1.4 g/cm³. The overall weight or basis weight ofthe fabric is often dictated by a desired opacity of the fabric topromote an acceptable thickness, strength and protection perception.

[0004] One reason for the increased usage of polyolefinic polymers(polypropylene and polyethylene) is that their bulk density issignificantly lower than polyester, polyamide and regenerated cellulosefiber. The polypropylene density is around 0.9 g/cm³, while theregenerated cellulose and polyester density values can be higher than1.35 g/cm³. The lower bulk density means that at equivalent basis weightand fiber diameter, more fibers are available to promote a thickness,strength and protection perception for the lower density polypropylene.Many of these attributes can be correlated with opacity. Therefore,manipulating the inherent opacity of the fiber and fabric in a consumerproduct can lead to better overall user acceptability.

[0005] A great deal of effort has been spent to address improve consumeracceptance by increasing the opacity of a fabric by reducing the overallfiber diameter. In woven fabrics, the spread of “microfiber” technologyfor improved softness and strength has become fashionable. In nonwovenfabrics, the use of “micro” fiber spunbond and meltblown technologieshas allowed improvements in opacity by reducing the fiber diameter.

[0006] The present invention has found that using hollow fibers providessubstantial improvements in opacity at equivalent outer fiber diameterand basis weight, through a reduction in overall bulk density of thefiber.

SUMMARY OF THE INVENTION

[0007] The present invention is directed to fibrous fabric comprisinghollow fibers. Preferably, the fibrous fabrics will have an opacitygreater than a fibrous fabric with an equivalent basis weight and madewith the same material and the same fiber diameter. The fibrous fabriccomprising hollow fibers may also have an opacity greater than a higherbasis weight fibrous fabric containing the same material and having anequivalent fiber diameter and the same number of fibers. The perimeterof the hollow region of the hollow fibers is substantiallynon-concentric to the outer perimeter of the hollow polymeric fibers.The hollow fibers can be monocomponent and multicomponent, as well asmonoconstituent or multiconstituent. These hollow fibers are thenconsolidated into woven and nonwoven fabrics that are then convertedinto articles.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawing where:

[0009]FIG. 1 illustrates a hollow fiber of the present invention.

[0010]FIG. 2 illustrates a concentric hollow fiber.

[0011]FIGS. 3, 4, 5, and 6 illustrate several variations ofnon-concentric hollow fiber of the present invention.

[0012]FIG. 7 is a photograph of a non-concentric hollow fiber of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0013] All percentages, ratios and proportions used herein are by weightpercent of the composition, unless otherwise specified. Examples in thepresent application are listed in parts of the total composition.

[0014] The specification contains a detailed description of (1)materials of the present invention, (2) configuration of the fibers, (3)material properties of the fibers, (4) processes, and (5) articles.

[0015] (1) Materials

[0016] Thermoplastic polymeric and non-thermoplastic polymeric materialsmay be used in the present invention. The thermoplastic polymericmaterial must have rheological characteristics suitable for meltspinning. The molecular weight of the polymer must be sufficiently highto enable entanglement between polymer molecules and yet low enough tobe melt spinnable. For melt spinning, thermoplastic polymers havingmolecular weights below 1,000,000 g/mol, preferably from about 5,000g/mol to about 750,000 g/mol, more preferable from about 10,000 g/mol toabout 500,000 g/mol and most preferably from about 50,000 g/mol to about400,000 g/mol.

[0017] The thermoplastic polymeric materials must be able to solidifyfairly rapidly, preferably under extensional flow, and form a thermallystable fiber structure, as typically encountered in known processes suchas a spin draw process for staple fibers or a spunbond continuousfilament process. Preferred polymeric materials include, but are notlimited to, polypropylene, polyethylene, polyester, polyamide,polyimide, polylactic acid, polyhydroxyalkanoate, polyvinyl alcohol,ethylene vinyl alcohol, polyacrylates, and copolymers thereof andmixtures thereof. Other suitable polymeric materials include ethyleneacrylic acid, polyolefin carboxylic acid copolymers, and combinationsthereof.

[0018] The hollow fibers of the present invention may be comprised of anon-thermoplastic polymeric material. Examples of non-thermoplasticpolymeric materials include, but are not limited to, viscose rayon,lyocell, cotton, wood pulp, regenerated cellulose, and mixtures thereof.The non-thermoplastic polymeric material may be produced via solution orsolvent spinning. The regenerated cellulose is produced by extrusionthrough capillaries into an acid coagulation bath.

[0019] Depending upon the specific polymer used, the process, and thefinal use of the fiber, more than one polymer may be desired. Thepolymers of the present invention are present in an amount to improvethe mechanical properties of the fiber, improve the processability ofthe melt, and improve attenuation of the fiber. The selection of thepolymer and amount of polymer will also determine if the fiber isthermally bondable and affect the softness and texture of the finalproduct.

[0020] Optionally, other ingredients may be incorporated into thespinnable composition. The optional materials may be used to modify theprocessability and/or to modify physical properties such as opacity,elasticity, tensile strength, wet strength, and modulus of the finalproduct. Other benefits include, but are not limited to, stabilityincluding oxidative stability, brightness, color, flexibility,resiliency, workability, processing aids, viscosity modifiers, and odorcontrol. Examples of optional materials include titanium dioxide,calcium carbonate, colored pigments, and combinations thereof. Furtheradditives including inorganic fillers such as the oxides of magnesium,aluminum, silicon, and titanium may be added as inexpensive fillers orprocessing aides. Other inorganic materials include hydrous magnesiumsilicate, titanium dioxide, calcium carbonate, clay, chalk, boronnitride, limestone, diatomaceous earth, mica glass quartz, and ceramics.Additionally, inorganic salts, including alkali metal salts, alkalineearth metal salts, phosphate salts, may be used.

[0021] (2) Configuration

[0022] The hollow fibers of the present invention will have a hollowregion. FIG. 1 illustrates a hollow fiber 10. The hollow region 20 has aperimeter 22. The solid region 30 of the hollow fiber 10 surrounds thehollow region 20. The perimeter of the hollow region 22 is also theinside perimeter of the solid region. The outside perimeter 32 of thesolid region 30 is also the outside perimeter of the hollow fiber 10.The circumscribed diameter of the hollow fiber may also be the outsideperimeter 32.

[0023] The hollow region is defined as the part of the fiber that doesnot contain the fiber material. It may also be described as the voidarea, void volume, or empty space. The hollow region may be filled withair or possibly a liquid. The hollow region will comprise from about 2%to about 60% of the fiber. Preferably, the hollow region will comprisefrom about 5% to about 40% of the fiber. More preferably, the hollowregion comprises from about 5% to about 30% of the fiber and mostpreferably from about 10% to about 30% of the fiber. The percentages aregiven for a cross sectional region of the hollow fiber (i.e. twodimensional). If described in three-dimensional terms, the percent voidvolume of the fiber will be equivalent to the percent of hollow region.

[0024] The percent of hollow region must be controlled for the presentinvention. The percent hollow is preferably not below 2% or the benefitof the hollow region is not significant. However, the hollow region mustnot be greater than 60% or the fiber may collapse. The desired percenthollow depends upon the materials used, the end use of the fiber, andother fiber characteristics and uses.

[0025] The fiber “diameter” of the hollow fiber of the present inventionis defined as the circumscribed diameter of the outer perimeter 32 ofthe hollow fiber. The diameter is not of the hollow region. Preferably,the hollow fiber will have a diameter of less than 100 micrometers. Morepreferably the fiber diameter will be from about 10 micrometers to about100 micrometers and preferably from about 10 micrometer to about 50micrometers. Fiber diameter is controlled by spinning speed, massthroughput, temperature, spinneret geometry, and blend composition,among other things.

[0026] Preferably, the hollow region of the hollow fibers will be of aparticular shape. The perimeter or outside edge of the cross section ofthe hollow region will be substantially non-concentric to the outerperimeter or outer edge of the solid region or hollow fiber. As usedherein, the term “non-concentric” is used to mean not having the samecenter point and/or not having the same shape or curvature (i.e. slopedifferential). Therefore, a hollow fiber is defined as beingnon-concentric if either the center point of the hollow region is notthe same as the center point of the hollow fiber or if the perimeter ofthe hollow region is not the same shape or curvature as the outsideperimeter of the hollow fiber. Most preferably, the shape of the hollowregion is substantially non-circular. For example, the hollow region maybe triangular or square in shape. The triangular or square shape willtypically have rounded edges.

[0027] Without being bound by theory, it is believed that the hollowcore allows for increased benefits in optical characteristics whichincrease opacity. The increase in opacity of the fibrous fabric may bedue to changes in at least one light characteristic selected from thegroup consisting of reflection, refraction, diffraction, absorption,scattering, and combinations thereof. This increase in opacity may beeven greater when the fibers are non-concentric hollow fibers versussolid fibers or concentric hollow fibers.

[0028]FIG. 2 is used to illustrate what is a concentric hollow fiber andnot a “non-concentric” hollow fiber. As shown, the center of the hollowregion and the center of the hollow fiber are the same. Additionally,the shape or curvature of the perimeter of the hollow region and thehollow fiber are the same. FIG. 3 illustrates non-concentric hollowfibers having several different shapes of the hollow region. Thesenon-concentric hollow fibers are illustrative of not having the samecurvature or shape in the hollow region as compared to the hollow fiber.As shown, these shapes may have straight or curved edges. Additionally,part of the perimeter of the hollow region may have the same curvatureas the hollow fiber as long as the entire curvature is not the same. Thehollow regions may or may not have the same center point as the hollowfiber. FIG. 4 illustrates that the shape of the hollow fiber need not becircular.

[0029]FIG. 5 illustrates other non-concentric hollow fibers where thehollow region does not have the same center point as the hollow fiber.The perimeter of the hollow region and the outer perimeter of the hollowfiber may be of the same curvature. FIG. 6 illustrates non-concentrichollow fiber having a variety of shapes for the hollow region. Thehollow region may contain one or more regions. FIG. 7 is a photographshowing a non-circular, partially square shaped, hollow region.

[0030] The mono and multiconstituent hollow fibers of the presentinvention may be in many different configurations. Constituent, as usedherein, is defined as meaning the chemical species of matter or thematerial. Fibers may be of monocomponent or multicomponent inconfiguration. Component, as used herein, is defined as a separate partof the fiber that has a spatial relationship to another part of thefiber.

[0031] The hollow fibers of the present invention may be multicomponenthollow fibers. Multicomponent fibers, commonly a bicomponent fiber, maybe in a side-by-side, sheath-core, segmented pie, ribbon, orislands-in-the-sea configuration. The sheath may be non-continuous orcontinuous around the core. The hollow fibers of the present inventionmay have different geometries that include round, elliptical, starshaped, rectangular, multi-lobal, and other various eccentricities. Thehollow regions in the fibers may be singular in number or multiple. Theholes may also be produced by dissolving out a water-soluble component,such as PVOH, EVOH and starch, for non-limiting examples.

[0032] (3) Material Properties

[0033] The fibrous fabrics of the present invention will have a basisweight and opacity that can be measured. Opacity can be measured usingTAPPI Test Method T 425 om-01 “Opacity of Paper (15/d geometry,Illuminant A/2 degrees, 89% Reflectance Backing and Paper Backing)”. Theopacity is measured as a percentage. The opacity of the fibrous fabriccontaining hollow fibers will be several percentage points of opacitygreater than the fibrous fabric containing solid fibers. The opacity maybe from about 2 to about 50 percentage points greater and commonly fromabout 4 to about 30 percentage points greater.

[0034] Basis weight is the mass per unit area of the substrate.Independent measurements of the mass and area of a specimen substrateare taken and calculation of the ratio of mass per unit area is made.Preferably, the basis weight of the fibrous fabrics of the presentinvention will be from about 4 grams per square meter (gsm) to about 70gsm depending upon the use of the fabric.

[0035] Additionally, the fibrous fabrics produced from the hollow fiberswill also exhibit certain mechanical properties, particularly, strength,flexibility, elasticity, extensibility, softness, thickness, andabsorbency. Measures of strength include dry and/or wet tensilestrength. Flexibility is related to stiffness and can attribute tosoftness. Softness is generally described as a physiologically perceivedattribute that is related to both flexibility and texture. Absorbencyrelates to the products' ability to take up fluids as well as thecapacity to retain them.

[0036] (4) Processes

[0037] The first step in producing a fiber is the compounding or mixingstep. In the compounding step, the raw materials are heated, typicallyunder shear. The shearing in the presence of heat will result in ahomogeneous melt with proper selection of the composition. The melt isthen placed in an extruder where the material is mixed and conveyedthrough capillaries and fibers are formed. A collection of fibers iscombined together using heat, pressure, chemical binder, mechanicalentanglement, hydraulic entanglement, and combinations thereof resultingin the formation of a nonwoven web or fabric. The nonwoven is thenassembled into an article. Alternatively, the fibers can be consolidatedtogether in a textile process to produce a woven web.

[0038] Equipment

[0039] The equipment used to produce the fibers in the examples camefrom one of three different types of spinning equipment. The smallest isa four-hole bicomponent spinline made by Hills Inc. The second line has82 holes and contains Hills Inc. bicomponent technology, modified froman original Alex James bicomponent spinline. The third line contains atleast 144 holes (nominally 288) and is located at Hills Inc, with theirbicomponent spinning technology. With these three small lines, fiber caneither be collected via mechanical winding at low or high speed. Thesefibers can then be mechanically drawn to further decrease theirdiameter. Heat is frequently used in the drawing process. These fibersare then crimped, if desired, and cut to the desired length. Thesefibers are then converted into a fabric.

[0040] Although the exact equipment is not important for manifesting theinvention of using hollow fiber in fabrics for better opacity, hollowfibers are typically produced using a special spinneret that divides thepolymer melt stream as it exits the spin pack. In the case of the HillsInc. spinneret technology, the melt stream is separated into foursegments that converge after the exit of the spinneret. Other designsmay make use of two or three segments that converge after exiting thespinneret. The size of the void can also be affected by pumping somelow-pressure gas into the void. The exact process for producing thefiber is not critical to this invention.

[0041] Spinning

[0042] The present invention utilizes the process of melt spinning inits most preferred embodiment. In melt spinning, there is no mass lossin the extrudate. Solution spinning may be used for producing fibersfrom cellulose, cellulosic derivatives, starch, and protein.

[0043] Spinning will occur at 100° C. to about 300° C. Fiber spinningspeeds of greater than 100 meters/minute are required. Preferably, thefiber spinning speed is from about 500 to about 14,000 meters/minute.The spinning may involve direct spinning, using techniques such asspunlaid or meltblown, as long as the fibers are mostly non-continuousin nature. Continuous fibers are hereby defined as having length towidth ratio greater than 5000. The fiber may also, be produced using aspin and draw technique, where the fiber is spun at a relatively slowspeed and mechanically drawn, with or without heat, to reduce the fiberdiameter.

[0044] Multiconstituent blends or polymeric materials can be melt spuninto fibers on conventional melt spinning equipment. The temperature forspinning ranges from about 100° C. to about 300° C. The processingtemperature is determined by the chemical nature, molecular weights andconcentration of each component. The fibers spun can be collected usingconventional godet winding systems or through air drag attenuationdevices. If the godet system is used, the fibers can be further orientedthrough post extrusion drawing at temperatures from about 50 to about200° C.

[0045] Multiconstituent blends may also be spun into fibers. Forexample, blends of polyethylene and polypropylene can be mixed and spunusing this technique. Another example would be blends of polyesters withdifferent viscosities or termonomer content. Multicomponent fibers canalso be produced that contain differentiable chemical species in eachcomponent.

[0046] The fibers and fabrics made in the present invention oftencontain a finish applied after formation to improve performance ortactile properties. These finishes typically are hydrophilic orhydrophobic in nature and are used to improve the performance ofarticles containing the finish. For example, Goulston Technologies'Lurol 9519 can be used with polypropylene and polyester to impart asemi-durable hydrophilic finish.

[0047] (5) Articles

[0048] The hollow fibers may be converted to fabrics by differentbonding methods. In a spunbond or meltblown process, the fibers areconsolidated using industry standard spunbond type technologies whilestaple fibers can be formed into a web using industry standard carding,airlaid, or wetlaid technologies. Typical bonding methods include:calender (pressure and heat), thru-air heat, mechanical entanglement,hydraulic entanglement, needle punching, and chemical bonding and/orresin bonding. Thermally bondable fibers are required for thepressurized heat and thru-air heat bonding methods. Fibers may also bewoven together to form sheets of fabric. This bonding technique is amethod of mechanical interlocking.

[0049] The hollow fibers of the present invention may also be bonded orcombined with thermoplastic or non-thermoplastic fibers to make nonwovenarticles. The thermoplastic polymeric fibers, typically syntheticfibers, or non-thermoplastic polymeric fibers, often natural fibers, maybe blended together in the forming process or used in discrete layers.Suitable synthetic fibers include fibers made from polypropylene,polyethylene, polyester, polyacrylates, and copolymers thereof andmixtures thereof. Natural fibers include lyocell and cellulosic fibersand derivatives thereof. Suitable cellulosic fibers include thosederived from any tree or vegetation, including hardwood fibers, softwoodfibers, hemp, and cotton. Also included are fibers made from processednatural cellulosic resources such as rayon.

[0050] The hollow fibers of the present invention may be used to makenonwovens, among other suitable articles. Nonwoven or fibrous fabricarticles are defined as articles that contains greater than 15% of aplurality of fibers that are non-continuous or continuous and physicallyand/or chemically attached to one another. The nonwoven may be combinedwith additional nonwovens or films to produce a layered product usedeither by itself or as a component in a complex combination of othermaterials, such as a baby diaper or feminine care pad. Preferredarticles are disposable, nonwoven articles. The resultant products mayfind use in filters for air, oil and water; vacuum cleaner filters;furnace filters; face masks; coffee filters, tea or coffee bags; thermalinsulation materials and sound insulation materials; nonwovens forone-time use sanitary products such as diapers, feminine pads, andincontinence articles; biodegradable textile fabrics for improvedmoisture absorption and softness of wear such as micro fiber orbreathable fabrics; an electrostatically charged, structured web forcollecting and removing dust; reinforcements and webs for hard grades ofpaper, such as wrapping paper, writing paper, newsprint, corrugatedpaper board, and webs for tissue grades of paper such as toilet paper,paper towel, napkins and facial tissue; medical uses such as surgicaldrapes, wound dressing, bandages, dermal patches and self-dissolvingsutures; and dental uses such as dental floss and toothbrush bristles.The fibrous web may also include odor absorbents, termite repellants,insecticides, rodenticides, and the like, for specific uses. Theresultant product absorbs water and oil and may find use in oil or waterspill clean-up, or controlled water retention and release foragricultural or horticultural applications. The resultant fibers orfiber webs may also be incorporated into other materials such as sawdust, wood pulp, plastics, and concrete, to form composite materials,which can be used as building materials such as walls, support beams,pressed boards, dry walls and backings, and ceiling tiles; other medicaluses such as casts, splints, and tongue depressors; and in fireplacelogs for decorative and/or burning purpose. Preferred articles of thepresent invention include disposable nonwovens for hygiene applications,such as facial cloths or cleansing cloths, and medical applications.Hygiene applications include wipes, such as baby wipes or femininewipes; diapers, particularly the top sheet or back sheet; and femininepads or products, particularly the top sheet. Other preferredapplications are wipes or cloths for hard surface cleansing. The wipesmay be wet or dry.

[0051] STAPLE FIBER EXAMPLES

[0052] The Examples below further illustrate the present invention. Thecrystalline PLA has an intrinsic viscosity of 0.97 dL/g with an opticalrotation of −14.2. The amorphous PLA has an intrinsic viscosity of 1.09dL/g with an optical rotation of −12.7. The poly(3-hydroxybutyrateco-alkanoate), PHA, has a molecular weight of 1,000,00 g/mol beforecompounding. The polyhydroxybutyrate (PHB) was purchased from Goodfellowas BU 396010. The polyvinyl alcohol copolymer (PVOH) was purchased fromAir Products Inc. and is a 2000 series polymer. One polypropylene waspurchased from FINA as FINA 3860×. Three polypropylenes were purchasedfrom Basell, Profax PH-835, Profax PDC-1298 and Profax PDC-1274. Thepolyethylene was purchased from Dow Chemical as Aspun 6811A. Fivepolyester resins were purchased from Eastman Chemical F61HC, 9663, 12822as well as two copolyester resins 14285 and 20110.

Comparative Example 1 Fibrous Web Containing Solid Fibers DryMeasurements

[0053] A polypropylene/Lyocell carded hydroentangled fabric was producedby blending 60 wt % of Basell PH-835 staple fibers with 40 wt % Lyocell.The Basell PH-835 fibers were spun, drawn and crimped to an averagefiber diameter of 20 μm. The Lyocell fiber is 1.5 d, roughly 12 μm indiameter. The following nonwoven fabrics were produced, along with theopacity of the nonwoven measured on the samples in which the basisweight was determined. Basis Weight Opacity (gsm) (%) 61.7 53.19 67.656.52 57.1 49.23 52.5 47.86 32.1 30.68 29.5 29.47

[0054] The opacity measurements are made on an Opacimeter Model BNL-3Serial Number 7628. Three measurements are made on one specimen.

Comparative Example 2 Fibrous Web Containing Solid Fibers WetMeasurements

[0055] A polypropylene/Lyocell carded hydroentangled fabric was producedby blending 60 wt % of Basell PH-835 staple fibers with 40 wt % Lyocell.The Basell PH-835 fibers were spun, drawn and crimped to an averagefiber diameter of 30 μm. The Lyocell fiber is 1.5 d, roughly 121 μm indiameter. The following nonwoven fabrics were produced and are measuredwet after addition of 315 wt % of water, along with the opacity of thenonwoven measured on the samples in which the basis weight wasdetermined. Dry Basis Weight Opacity (gsm) (%) 61.8 41.0 63.8 41.8 65.941.4

[0056] The opacity measurements are made on an Opacimeter Model BNL-3Serial Number 7628.

[0057] Three measurements are made on one specimen.

Example 1 Fibrous Web Containing Non-Concentric Hollow Fibers DryMeasurements

[0058] A polypropylene/Lyocell carded hydroentangled fabric was producedby blending 60 wt % of Basell PH-835 hollow staple fibers with 40 wt %Lyocell. The percent void area of the Basell PH-835 hollow staple fibersis 20%. The Basell PH-835 fibers were spun, drawn and crimped to anaverage fiber diameter of 20 μm. The Lyocell fiber is 1.5 d, roughly 12μm in diameter. The following nonwoven fabrics were produced, along withthe opacity of the nonwoven measured on the samples in which the basisweight was determined. Basis Weight Opacity (gsm) (%) 49.1 55.07 55.858.17 55.5 57.93 56.4 61.11 47.7 54.06 46.8 53.54 30.6 40.54 25.9 34.82

[0059] The opacity measurements are made on an Opacimeter Model BNL-3Serial Number 7628. Three measurements are made on one specimen.

[0060] The increase in opacity as shown in this example versusComparative Example 1 can be seen with this data. The following graphillustrates this difference.

Example 2 Fibrous Web Containing Non-Concentric Hollow Fibers WetMeasurements

[0061] A polypropylene/Lyocell carded hydroentangled fabric was producedby blending 60 wt % of Basell PH-835 hollow staple fibers with 40 wt %Lyocell. The Basell PH-835 fibers were spun, drawn and crimped to anaverage fiber diameter of 30 μm. The percent void area of the BasellPH-835 hollow staple fibers is 15%. The Lyocell fiber is 1.5 d, roughly12 μm in diameter. The following nonwoven fabrics were produced and aremeasured wet after addition of 315 wt % of water, along with the opacityof the nonwoven measured on the samples in which the basis weight wasdetermined. Dry Basis Weight Opacity (gsm) (%) 61.8 47.8 64.2 50.1 66.451.5

[0062] The opacity measurements are made on an Opacimeter Model BNL-3Serial Number 7628. Three measurements are made on one specimen.

[0063] The increase in opacity as shown in this example versusComparative Example 2 can be seen.

Example 3-22

[0064] The following table provides examples of fibers and fabricscomposed of various polymers. Examples 3-11 illustrate single componentfibers and Examples 12-22 illustrate bicomponent fibers. The bicomponentfibers typically have a sheath to core ratio of from about 20:80 toabout 80:20. The fibers are produced either a direct spin process orspin and draw process. The table also provides the void volume of thehollow region. The void volumes ranges can be made depending on the massthrough-put per hole and melt temperature. As the mass through-putincreases and as the melt temperature decreases, the void volumegenerally increases. These fiber can be blended with other syntheticstaple fibers or regenerated cellulose fibers. Example Number PolymerVoid volume 3 PLA - Biomer L9000 5-25% 4 Basell PDC-1274 5-30% 5 BasellPDC-1298 5-40% 6 Dow Aspun 6811A 5-20% 7 Eastman F61HC 5-20% 8 Eastman9663 5-35% 9 Eastman 12822 5-40% 10 Eastman 14285 5-35% 11 Eastman 201105-25% 12 Sheath - Dow Aspun 6811A 5-25% Core - Basell PH-835 13 Sheath -Dow Aspun 6811A 5-35% Core - Basell PDC-1274 14 Sheath - Dow Aspun 6811A5-25% Core - Eastman F61HC 15 Sheath - Basell PH-835 5-25% Core -Eastman F61HC 16 Sheath - Eastman 20110 5-25% Core - Eastman F61HC 17Sheath - Dow Aspun 6811A 5-25% Core - Eastman 9663 18 Sheath - Eastman14285 5-25% Core - Eastman F61HC 19 Sheath - Eastman 14285 5-30% Core -Eastman 9663 20 Sheath - Eastman 14285 5-30% Core - Basell PDC-1274 21Sheath - Biomer L9000 5-30% Core - Basell PDC-1274 22 Sheath - BasellPH-835 5-30% Core - Basell PDC-1274

[0065] Many examples have been shown and given here to demonstrate thebreadth of fibers that can be produced to illustrate the invention. Thebenefit of the hollow fibers of the present invention is demonstratedusing Graph 1. Graph 1 shows a plot of Opacity vs Basis Weight forComparative Example 1 and Example 1.

[0066] Graph 1 shows that for the same resin, Basell PH-835, that hollowfibers have better opacity at equivalent basis weight than solid fibers.Another way of interpreting the Graph 1 is to say that the basis weightof the hollow fabric can be reduced from 58 gsm to 44 gsm and maintainthe same level of opacity.

[0067] Continuous Fiber Examples

[0068] The Examples below further illustrate the present invention. Thecrystalline PLA was purchased from Biomer as Biomer L9000. The amorphousPLA was purchased from Birmingham Polymer and has an intrinsic viscosityof 1.09 dL/g with an optical rotation of −12.7. The poly(3-hydroxybutyrate co-alkanoate), PHA, has a molecular weight of1,000,00 g/mol before compounding. The polyhydroxybutyrate (PHB) waspurchased from Goodfellow as BU 396010. The polyvinyl alcohol copolymer(PVOH) was purchased from Air Products Inc. and is a 2000 seriespolymer. One polypropylene was purchased from FINA as FINA 3860×. Threepolypropylenes were purchased from Basell, Profax PH-835, ProfaxPDC-1298 and Profax PDC-1274. The polyethylene was purchased from DowChemical as Aspun 6811A. Five polyester resins were purchased fromEastman Chemical F61HC, 9663, 12822 as well as two copolyester resins14285 and 20110.

Comparative Example 23 Fibrous Web Containing Solid Fibers

[0069] A polypropylene spunbond fabric was produced using solid fibermade from Basell PH-835. The through-put per hole was 0.65 ghm using2016 hole spinneret. The fibers were attenuated to an average fiberdiameter of 14 μm. These fibers were thermally bonded together usingheat and pressure. The following nonwoven fabrics were produced, alongwith the opacity of the nonwoven measured on the samples in which thebasis weight was determined. Basis Weight Opacity (gsm) (%) 25.9 ± 1.326.4 ± 2.8 24.2 ± 1.7 23.8 ± 2.5 17.6 ± 0.4 18.5 ± 1.7

[0070] The opacity measurements are made on an Opacimeter Model BNL-3Serial Number 7628. Three measurements are made on one specimen. Thedata presented here is the average of three specimens for each material.

Comparative Example 24 Fibrous Web Containing Solid Fibers

[0071] A polypropylene spunbond fabric was produced using solid fibermade from Basell PH-835. The through-put per holes was 0.65 ghm using2016 hole spinneret. The fiber were attenuated to an average fiberdiameter of 16 μm. These fibers were thermally bonded together usingheat and pressure. The following nonwoven fabrics were produced, alongwith the opacity of the nonwoven measured on the samples in which thebasis weight was determined. Basis Weight Opacity (gsm) (%) 21.1 ± 1.118.5 ± 1.7 25.9 ± 1.3 23.8 ± 2.8

[0072] The opacity measurements are made on an Opacimeter Model BNL-3Serial Number 7628. Three measurements are made on one specimen. Thedata presented here is the average of three specimens for each material.

Comparative Example 25 Fibrous Web Containing Solid Fibers

[0073] A polypropylene spunbond fabric was produced using solid fibermade from FINA 3860×. The through-put per holes was 0.40 ghm using 2016hole spinneret. The fibers were attenuated to an average fiber diameterof 13 μm. The following nonwoven fabrics were produced, along with theopacity of the nonwoven measured on the samples in which the basisweight was determined. Basis Weight Opacity (gsm) (%) 20.8 ± 1.3 21.7 ±4.7 18.3 ± 1.7 18.8 ± 2.3 16.7 ± 0.4 16.4 ± 4.2

[0074] The opacity measurements are made on an Opacimeter Model BNL-3Serial Number 7628. Three measurements are made on one specimen. Thedata presented here is the average of three specimens for each material.

Example 23 Fibrous Web Containing Hollow Fibers

[0075] A polypropylene spunbond fabric was produced using hollow fibersmade from Basell PH-835. The through-put per holes was 0.40 ghm using1008 hole spinneret. The fibers were attenuated to an average fiberdiameter of 17 μm. These fibers have an average void volume of 20%. Thefollowing nonwoven fabrics were produced, along with the opacity of thenonwoven measured on the samples in which the basis weight wasdetermined. Basis Weight Opacity (gsm) (%) 18.7 ± 1.2 23.7 ± 1.8 16.3 ±0.8 20.0 ± 2.0

[0076] The opacity measurements are made on an Opacimeter Model BNL-3Serial Number 7628. Three measurements are made on one specimen. Thedata presented here is the average of three specimens for each material.

Example 24 Fibrous Web Containing Hollow Fibers

[0077] A polypropylene spunbond fabric was produced using hollow fibersmade from Basell PH-835. The through-put per holes was 0.40 ghm using1008 hole spinneret. The fibers were attenuated to an average fiberdiameter of 19 μm. These fibers have an average void volume of 20%. Thefollowing nonwoven fabrics were produced, along with the opacity of thenonwoven measured on the samples in which the basis weight wasdetermined. Basis Weight Opacity (gsm) (%) 22.2 ± 1.2 26.9 ± 1.8 18.7 ±0.8 23.5 ± 2.0 16.3 ± 1.2 20.0 ± 1.8 13.9 ± 0.8 17.2 ± 2.0

[0078] The opacity measurements are made on an Opacimeter Model BNL-3Serial Number 7628. Three measurements are made on one specimen. Thedata presented here is the average of three specimens for each material.

Example 25-44

[0079] The following table provides examples of continuous fibers andfabrics composed of various polymers. Examples 25-33 illustrate singlecomponent fibers and Examples 34-44 illustrate bicomponent fibers. Thebicomponent fibers typically have a sheath to core ratio of from about20:80 to about 80:20. The fibers are produced either a direct spinprocess or spin and draw process. The table also provides the voidvolume of the hollow region. The void volumes ranges can be madedepending on the mass through-put per hole and melt temperature. As themass through-put increases and as the melt temperature decreases, thevoid volume generally increases. Example Number Polymer Void volume 25PLA - Biomer L9000 5-25% 26 Basell PDC-1274 5-30% 27 Basell PDC-12985-40% 28 Dow Aspun 6811A 5-20% 29 Eastman F61HC 5-20% 30 Eastman 96635-35% 31 Eastman 12822 5-40% 32 Eastman 14285 5-35% 33 Eastman 201105-25% 34 Sheath - Dow Aspun 6811A 5-25% Core - Basell PH-835 35 Sheath -Dow Aspun 6811A 5-35% Core - Basell PDC-1274 36 Sheath - Dow Aspun 6811A5-25% Core - Eastman F61HC 37 Sheath - Basell PH-835 5-25% Core -Eastman F61HC 38 Sheath - Eastman 20110 5-25% Core - Eastman F61HC 39Sheath - Dow Aspun 6811A 5-25% Core - Eastman 9663 40 Sheath - Eastman14285 5-25% Core - Eastman F61HC 41 Sheath - Eastman 14285 5-30% Core -Eastman 9663 42 Sheath - Eastman 14285 5-30% Core - Basell PDC-1274 43Sheath - Biomer L9000 5-30% Core - Basell PDC-1274 44 Sheath - BasellPH-835 5-30% Core - Basell PDC-1274

[0080] Many examples have been shown and given here to demonstrate thebreadth of fibers can be produced to illustrate the invention. Thebenefit of the invention can be shown g two graphs. Graph 2 shows a plotof Opacity vs Basis Weight for Comparative Example 24 and Example 23.One additional data point has been added for each, the requirement thatthe opacity at zero basis weight is zero. The data in Graph 3 shows acomposite plot of Comparative Example 23, Comparative Example 25 andExample 24.

[0081] Graph 2 shows that for the same resin, Basell PH-835, thatslightly larger diameter hollow fibers have better opacity at equivalentbasis weight than solid fibers. Another way of interpreting the Graph 2shows that the basis weight of the hollow fabric can be reduced from 20gsm to 14 gsm and maintain the same level of opacity.

[0082] Graph 3 illustrates the full effect of the invention. The muchsmaller solid fiber produced with FINA 3860× and Basell PH-835 do notmatch the opacity of a nonwoven produced with larger diameter hollowfibers made with Basell PH-835. This graph shows that the basis weightof the hollow fiber fabric can be reduced from 20 gsm to 16 gsm andmatch the much smaller diameter fabric.

[0083] The disclosures of all patents, patent applications (and anypatents which issue thereon, as well as any corresponding publishedforeign patent applications), and publications mentioned throughout thisdescription are hereby incorporated by reference herein. It is expresslynot admitted, however, that any of the documents incorporated byreference herein teach or disclose the present invention.

[0084] While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is intended tocover in the appended claims all such changes and modifications that arewithin the scope of the invention.

What is claimed is:
 1. A fibrous fabric comprising hollow polymericfibers comprising an outer perimeter and a hollow region having aperimeter, wherein the perimeter of the hollow region is substantiallynon-concentric to the outer perimeter of the hollow polymeric fiber. 2.The fibrous fabric of claim 1, wherein the perimeter of the hollowregion of the hollow polymeric fibers is substantially non-circular. 3.The fibrous fabric of claim 1, wherein the hollow region of the hollowpolymeric fiber is from about 5% to about 40%.
 4. The fibrous fabric ofclaim 1, wherein the hollow polymeric fiber has a diameter of from about10 microns to about 100 microns.
 5. The fibrous fabric of claim 1,wherein the hollow polymeric fiber is comprised of a thermoplasticpolymeric material selected from the group consisting of polypropylene,polyethylene, polyester, polyamide, polyimide, polylactic acid,polyhydroxyalkanoate, polyvinyl alcohol, polyacrylates, and mixturesthereof.
 6. The fibrous fabric of claim 1, wherein the hollow polymericfiber is comprised of a non-thermoplastic material selected from thegroup consisting of viscose rayon, lyocell, cotton, wood pulp, andmixtures thereof.
 7. The fibrous fabric of claim 1, wherein thepolymeric material is blended with particulates comprised of materialsselected from the group consisting of titanium dioxide, calciumcarbonate, colored pigments, and mixtures thereof.
 8. The fibrous fabricof claim 5, wherein the hollow polymeric fiber is blended withnon-thermoplastic polymeric fibers.
 9. The fibrous fabric of claim 8,wherein the non-thermoplastic polymeric fibers have a hollow region. 10.The fibrous fabric of claim 9, wherein a perimeter of the hollow regionof the hollow non-thermoplastic polymeric fibers is substantiallynon-concentric to an outer perimeter of the hollow non-thermoplasticpolymeric fibers.
 11. A fibrous fabric comprising hollow polymericfibers which comprise a polymeric material and have a hollow region,wherein the fibrous fabric has an opacity greater than a fibrous fabricproduced with the same polymeric material at an equivalent fiberdiameter and basis weight.
 12. The fibrous fabric of claim 11, whereinthe hollow region has a perimeter and the perimeter of the hollow regionis substantially non-concentric to an outer perimeter of the hollowpolymeric fibers.
 13. The fibrous fabric of claim 11, wherein theperimeter of the hollow region of the hollow polymeric fibers issubstantially non-circular.
 14. A wet wipe comprising the fibrous fabricof claim
 1. 15. The wet wipe of claim 14 having a wet opacity greaterthan a wet wipe comprising the same polymeric material at an equivalentfiber diameter and basis weight.
 16. A wet wipe comprising the fibrousfabric of claim
 10. 17. The wet wipe of claim 16 that has a wet opacitygreater than a wet wipe comprising the same polymeric material at anequivalent fiber diameter and basis weight.
 18. The fibrous fabric ofclaim 1 wherein the fibrous fabric has an opacity greater than a fibrousfabric comprising concentric hollow fibers comprising the same materialand having an equivalent fiber diameter and basis weight.
 19. Thefibrous fabric of claim 10 wherein the fibrous fabric has an opacitygreater than a fibrous fabric comprising concentric hollow fiberscomprising the same material and having an equivalent fiber diameter andbasis weight.
 20. The fibrous fabric of claim 1 wherein the hollowpolymeric fiber has a multicomponent configuration.